For me, the hands-down winner would be the Honda over the Briggs. As it happens, it's even less expensive to buy. Your tiller is geared down to drive the tines at less than 10 percent of the engine's speed at wide open throttle. That means the torque and hp of the engine are more than ten times greater as far as the tines are concerned.

If your old engine did a good job when it was new, then there is no real reason to increase the hp because all you are increasing is the amount of fuel you will burn each time out.

If you find those engines too expensive, you might want to consider a Honda clone from places such as Harbour Freight. After all, most people don't even put ten hours per season on their tillers.